A latch of a wearable smart device such as a smart wristwatch and a smart bracelet in the related art is assembled onto a watchband via a spring bar. The assembly process is as follows. One end of the spring bar is inserted into a fixing hole of a watch frame, and the end of the spring bar is pressed by using tweezers to slowly approach another fixing hole of the watch frame, and then the end of the spring bar is inserted into the fixing hole of the watch frame under the action of a spring after loosening the tweezers. However, due to over-pressure during assembly, the elasticity of the spring bar may be influenced, and the reliability of the spring bar may be reduced. In addition, the fixing hole of the watch frame is not easily aligned during assembly, thereby resulting in assembly inflexibility. Moreover, the space of the spring bar after assembly is small, and if the force of the spring is small, the spring bar may be disengaged from the fixing hole of the watch frame. That is to say, the structural form of a conventional latch has the problems of poor reliability, inflexible assembly and disassembly, and the like.